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Does an older Cement Block Home Provide Adequate Insulation?

jdom | Posted in Energy, Heating & Insulation on July 14, 2011 10:02am

Hi All – I realize that “adequate” can be subjective, but here’s the situation.  My daughter is looking to purchase a home here in Southeast Pennsylvania.  She likes a house that we recently took a look at.  It’s a ranch, about 1700sqft, and appears to have cement block exterior walls.  I based this conclusion on a couple of observations; the wall in the attached garage is cement block, and the window casings appear to be about 10 inches wide.  The exterior finish is mostly stucco, with stone (facade?) on about 1/3 of the front of the building.  It was built in the early 50’s.  I’ve done some research and I’m a bit concerned about the insullation value of these walls.  If my research is correct, the blocks have an R-value of about 1.  I assume that there is a 2×4 frame on the interior, so, assuming that was insullated reasonably well, that still means (by my calculation) only about an R-12 for the walls.  That concerns me because it doesn’t seem particularly well insullated by today’s standards.  Am I missing something here?  Would they generally have taken additional steps to insulate a block wall back in the 50’s? Any ideas on an easy way to verify the makeup of the walls if we take another look at the house?

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  1. DanH | Jul 14, 2011 10:23pm | #1

    3" of fiberglass insulation

    3" of fiberglass insulation would have been considered excellent back in the 50s.  In fact, that's all we have in this house, built in 1976 in southern Minnesota, and it's quite enough to keep us comfortable in sub-zero weather.  (Of course, you can't depend on the walls being insulated at all if the house was built in the 50s.)  Of more importance, probably, is the amount of attic insulation (though that's easier to rectify if deficient).

    A concrete block building is good in that there's much less opportunity for infiltration vs a wood-sided wall, and the concrete block itself provides R1-R2 additional insulation.

    You can at least get an idea of the insulation in the walls if you remove a few outlet covers and can manage to see around the edge of the outlet box to the inside of the wall.  Or sometimes you'll find an access panel under a sink or near the breaker panel (which likely would have begun life as a fuse box).

    Remember that in a 50s home another thing you want to be concerned about is the wiring.  If the place has never been professionally rewired there's almost certainly some jury-rigged wiring that's suspect.

  2. davidmeiland | Jul 15, 2011 03:13am | #2

    More insulation

    Tough situation, but more insulation in that scenario would probably be in the form of exterior foam installed over the block, followed by new siding. Not a lot different than beefing up a wood framed wall, actually. There is the possibility of urea formaldehyde foam insulation (UFFI) poured into the block cells when the house was built, I suppose, depending on local practice. Dan is right that the attic would be the first target.

  3. florida | Jul 15, 2011 07:49am | #3

    I expect R-12 is wildly optimistic. Insulation loses R value as it ages and houses built diring the 50's weren't generally insulated well to begin with. The walls probably have a couple of inchs of mineral wool that has sagged and wasn't placed with much care to begin with. The attic may have a couple of inches of Vermiculite or fiberglass. You can add insulation to the attic pretty cheaply but the walls will be costly. There's not much point in spending a bundle on wall insulation and leaving the old, drafty original windows so you'd want to include those as well. Fuel oil was cheap back then so nobody spent much time on sealing air leaks or insulation.

    1. DanH | Jul 15, 2011 07:57am | #4

      It should be noted that SE Pennsylvania is not an arctic climate.

      I'd ask for records of heating costs for the past 2 years (be sure to include electric, in case they were using space heaters), and also check the attic insulation.  Then decide if it's an affordable place to live (possibly with added attic insulation).  If not, pass on it -- don't plan on updating the wall insulation.

      [Got to thinking:  Concrete block of that era would likely have had steel casement windows.  Is that the case?  What are the windows like?]

      1. jdom | Jul 15, 2011 10:28am | #5

        Reply

        Everyone - Thanks for the insights! 

        Dan - Although I didn't examine them closely, I'm pretty sure that all of the windows were wood.  They just had the obvious look of weathered, peeling, wood, with wood storms on the outside of each.  So I assumed they were original and would need to be replaced.  We're going to look at the house again on Sunday.  I'm going to take a closer look at them, and also see if I can do a bit of probing through (around) an electrical outlet or two as suggested. 

    2. Clewless1 | Aug 04, 2011 12:55am | #9

      Generally insulation does NOT lose R-value w/ age ... it may lose R-value as it sags or shifts w/ age, but generally the R-value per inch remains constant. If installed properly, it shouldn't shift or sag, really, but bad installs may be conducive to shifting and sagging .. then the construction loses R-value/effectiveness, but the insulation in and of itself would not, really.

      1. gfretwell | Aug 04, 2011 01:48am | #10

        Cellulose seems to turn to crap here over time. My attic had about 8" of cellulose blown in it around 1980 and now it is just 2" of  grey dust.. I think a big part of the problem is that the whole vapor barrier thing is backward when you are in the sub-tropics. The warm moist air that you are supposed to put the vapor barrier against is in the attic, not the house, most of the year.

        When the A/C is on, that blown in cellulose is just a moisture trap and it rots out.

        1. DanH | Aug 04, 2011 06:57am | #11

          Of course, 8 inches of loose cellulose would be expected to compact down to 4-5 over time.

        2. Clewless1 | Aug 04, 2011 08:08am | #12

          Good points. Maybe there is such a thing as a bad batch of cellulose, too. I've not heard anything about cellulose absorbing moisture in warm high humid areas. It is just paper. Wonder if it acts as a desiccant.

  4. gfretwell | Jul 15, 2011 12:42pm | #6

    Block is a horrible insulator. I am in a CBS house here (Fla) and we have an addition on the back with separate HVAC I seldom turn on. I insulated that some but the existing wall between is the regular CBS. That room stays cool, just from the thermal leakage from the house. It is an eye opener about how bad a CBS wall is.

    I bet you have 3/4" furring and zero insulation in that house based on your guess that the window holes are about 10" deep.

    8" block (7 5/8") 1/2" stucco, 3/4" furring, 1/2" drywall = 9 3/8"

    1. jdom | Jul 15, 2011 07:22pm | #7

      Block is Horrible

      That would be scary!  But I don't know how the outlets would fit if there was only 3/4" of space behind the drywall.  I will definately take a close look at the situation on Sunday.  Thanks!

      1. gfretwell | Jul 16, 2011 02:11pm | #8

        They knock holes in the block and set the boxes in the hole, flush with the drywall. They make boxes for the purpose and there is a 1/2" KO so you can run an EMT up the wall. It used to be accepted as code that the wire had to be protected if it was not 1.25" back from the drywall. Now they let that be sideways on a "stacker". (bad decision)

  5. Nailgunner | Aug 05, 2011 01:48pm | #13

    I have a 50's home very similiar to the one mentioned, the exterior wall studs are 2x2, fiberglass insulation, on slab construction. Wiring is old two wire copper. As mentioned in the previous post(s), the block is very good in regard to reducing air infilrtration and insulation values overhead really matter. One factor I would add is the quality of the windows, mine were original aluminuim frame and about -2 on the r-value. The block construction is a great place to ride out a tornado here in Arkansas.

  6. Clewless1 | Aug 12, 2011 05:18pm | #14

    No it wasn't 'exactly what you said'. You must have misread my post.

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